1. Field of the Invention
The present invention relates to an image forming apparatus for recording image information on a record material (sheet) or the recording apparatus thereof, in particular, to a recording apparatus using an ink jet recording system for spraying ink corresponding to a signal.
2. Related Background Art
Conventionally, image forming apparatus (recording apparatuses) for use as printers, copiers, facsimile machines, and so forth drive an energy generating member for a record head corresponding to image information received so as to record a dot pattern image on a record material such as a piece of paper or a plastic sheet.
However, in addition to such an ink jet recording system, wire-dot systems, thermal systems, laser beam systems, and so forth are known. Next, with reference to FIG. 23, an ink jet recording system will be described. A record head 351 discharges ink on a record paper sheet P corresponding to image information so as to record the image on the record paper sheet P. The record head 351 is disposed on a carriage 352. The carriage 352 is connected to a lead screw 353. The lead screw 353 is rotated by a drive source (not shown) so as to reciprocate the carriage 352 along a guide shaft 354 (perpendicular to the plane of the drawing). While the carriage 352 is moved, the record head 351 is driven so as to discharge ink on the record paper sheet P.
A conveying means conveys the record paper sheet P to the record head 351. The conveying means has a conveying roller 355 and a pinch roller 356. The conveying roller 355 is disposed on the rear side of the record paper sheet P. The pinch roller 356 pinches the record paper sheet P along with the conveying roller 355. Thus, the record paper sheet P pinched by the conveying roller 355 and the pinch roller 356 is conveyed to a support table (platen) disposed at a record position. The conveying roller 355 is disposed on a drive side (drive force is received and thereby rotated). The surface of the conveying roller 355 is coated with a high frictional material (for example, rubber). In addition, the pinch roller 356 is disposed on a follower side (rotated by the conveying roller 355). The pinch roller 356 is for example a metal roller. Both ends of a rotating shaft of the pinch roller 356 are tensioned by a pair of leaf springs 357. Thus, the pinch roller 356 presses the conveying roller 355.
The distance between the record head 351 and the front surface of the record paper sheet P is given by: EQU .delta.=.delta..sub.0 -t
where .delta. is the distance (record head distance) between the record head 351 and the front surface of the record sheet P; and .delta..sub.0 is the distance between the record head 351 and the support table. Thus, the ink spray distance varies corresponding to t. Consequently, the position of the record head 351 or conveying roller 355 should be adjusted corresponding to the sheet thickness t.